RMIF

Rotate, mask insert flags

This instruction performs a rotation right of a value held in a general-purpose register by an immediate value, and then inserts a selection of the bottom four bits of the result of the rotation into the PSTATE flags, under the control of a second immediate mask.

Encoding: Integer

Variants: FEAT_FlagM (ARMv8.4)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	0	1	1	1	0	1	0	0	0	0							0	0	0	0	1						0
sf	op	S									imm6											Rn					o2	mask

RMIF <Xn>, #<shift>, #<mask>

Decoding algorithm

if !IsFeatureImplemented(FEAT_FlagM) then EndOfDecode(Decode_UNDEF);
constant integer imm = UInt(imm6);
constant bits(4) flagmask = mask;
constant integer n = UInt(Rn);

Operation

constant bits(64) reg = X[n, 64];
constant bits(4) flags = (reg:reg);
if flagmask<3> == '1' then PSTATE.N = flags<3>;
if flagmask<2> == '1' then PSTATE.Z = flags<2>;
if flagmask<1> == '1' then PSTATE.C = flags<1>;
if flagmask<0> == '1' then PSTATE.V = flags<0>;

Explanations

<Xn>: Is the 64-bit name of the general-purpose source register, encoded in the "Rn" field.
<shift>: Is the shift amount, in the range 0 to 63, defaulting to 0 and encoded in the "imm6" field.
<mask>: Is the flag bit mask, an immediate in the range 0 to 15, which selects the bits that are inserted into the NZCV condition flags, encoded in the "mask" field.

Operational Notes

If PSTATE.DIT is 1:

• The execution time of this instruction is independent of:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.